Why this Stores Procedure is not working - puzzled

Here is the SP:
--#SET TERMINATOR !
CREATE PROCEDURE execute_immediate (IN in_stmt VARCHAR(1000)
,OUT out_sqlcode INTEGER)
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
DECLARE sqlcode INTEGER;
DECLARE EXIT HANDLER FOR sqlexception
SET out_sqlcode = sqlcode;
EXECUTE IMMEDIATE in_stmt;
SET out_sqlcode = sqlcode;
RETURN;
END!

I have field HIREDATE char(10)
SELECT DATE( HIREDATE) FROM EMP_SCREEN_EDIT;
1         
----------
12/27/1999

  1 record(s) selected.
I updated Hiredate using SP - Maked it invalid: 
CALL execute_immediate('UPDATE  EMP_SCREEN_EDIT SET HIREDATE =
''12/77/1999''',?)

  Value of output parameters
  --------------------------
  Parameter Name  : OUT_SQLCODE
  Parameter Value : 0

  Return Status = 0


After Update:
SELECT HIREDATE FROM EMP_SCREEN_EDIT

HIREDATE  
----------
12/77/1999

SELECT DATE(HIREDATE) FROM EMP_SCREEN_EDIT
the string representation of a datetime value is out of range
sqlcode: -181

Now 2 selects using SP:

CALL execute_immediate('SELECT HIREDATE FROM EMP_SCREEN_EDIT',?)

  Value of output parameters
  --------------------------
  Parameter Name  : OUT_SQLCODE
  Parameter Value : -84

  Return Status = 0

 CALL execute_immediate('SELECT DATE(HIREDATE) FROM EMP_SCREEN_EDIT',?)

  Value of output parameters
  --------------------------
  Parameter Name  : OUT_SQLCODE
  Parameter Value : -84

  Return Status = 0

Why Stored Procedure returns in both cases  -84
What is going on???

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